Medium/high voltage incandescent lamp and reflector combination

ABSTRACT

A reflector incandescent lamp for high-voltage operation has substantiallyxially parallel radiant body sections and a reflector, whose facets are formed by approximately axially parallel cylindrical segments.

FIELD OF THE INVENTION

The invention relates to a reflector incandescent lamp combinationhaving an at least substantially axially arranged radiant body.

BACKGROUND

A reflector lamp is described in U.S. Pat. No. 4,021,659, Wiley. Thelamp described there has an axial coil and facets which are either flator curved in convex fashion. The homogeneity of the light distributionin such lamps is not satisfactory for all applications, however. Aboveall, such a design is only conditionally suitable for medium- andhigh-voltage lamps (typically, the practical lower limit is 80 V), sincethen, compared to the low-voltage range, the radiant bodies must bechosen to be very long, and often they are divided into a plurality ofsections.

THE INVENTION

The object of the present invention is to improve the homogeneity of thelight projected by reflector incandescent lamps which, in particular,are operated at medium or high voltage, that is, above 80 V.

Briefly, the lamp of the lamp-reflector combination has a radiant bodywhich is oriented substantially axially or axially-parallel with respectto the reflector, in which the lamp is also, preferably securely,mounted. The reflector has a reflective surface which is formedsubstantially of trapezoid-like facets. The majority of the facets areformed as concavely curved cylindrical surfaces with an associated axisof symmetry, each axis of symmetry being located in a plane whichincludes the reflector axis. The radiant body of the lamp has at leasttwo luminous sections, and the luminous sections are so located in thelamp that, with respect to the reflector, they are approximately axiallyparallel to the reflector axis, but do not coincide with the reflectoraxis.

It has been found that the homogeneity of the illumination, especiallyin lamps with multiple radiant body sections, can be improvedconsiderably if the facets of the reflector comprise concex cylindricalsegments. It is essential, however, for the axes of the cylindricalsegments to be oriented such that they are located in planes thatinclude the reflector axis. In particular, these axes should be orientedapproximately parallel to the reflector axis. "Convex" is to beunderstood with reference to the optically active side of the reflector.

Conversely, it has been found that cylindrical segments whose axes aretransverse to the reflector axis exhibit major nonhomogeneities ofillumination.

The particular advantage of the cylindrical segments of the invention isthat as a result, not only lamps with an axial radiant body (especiallylow-voltage lamps) but also lamps whose radiant bodies are composed of aplurality of approximately axially parallel sections, especially high-and medium-voltage lamps (generally understood to mean voltages above 80V), that provide homogeneous illumination can be furnished. To achievean homogeneous illumination, the individual sections of the radiant bodyare inclined by no more than 15° and preferably at most 10° from thereflector axis. Examples are V shapes W shapes or the like, andespecially shapes that are varied in mirror symmetry to them, such as Uand M shapes.

In particular, through the characteristics of the invention, even verycompact reflector lamps can be made. A halogen incandescent lamp isadvantageously used for the purpose. In particular, its structurallength can be decreased further by dispensing with a quartz beam for themount that holds the radiant body. The mount parts are retained directlyin a pinch seal. Instead of being held by a mount (or in addition toit), the radiant body can also be retained by deformations of the bulbsee U.S. Pat. No. 5,146,134, Stadler et al..

DRAWINGS

An exemplary embodiment will be described in further detail below. Shownare

FIG. 1, a reflector incandescent lamp combination with axially parallelcylindrical facets;

FIG. 2, a cross section through the reflector;

FIG. 3, the light distribution of the lamp of FIG. 1;

FIG. 4, the light distribution of a lamp with cylindrical facets lyingtransversely;

FIG. 5, a further embodiment of a lamp.

FIG. 1 shows a reflector incandescent lamp 1 for general lightingpurposes. It comprises a high-voltage (230 V) halogen incandescent lamp2 with an output of 50 W, which is secured via two long power leads inthe apex of a pressed glass reflector 3, which has a diameter of 63 mm(PAR 20) or 95 mm (PAR 30), for example. The reflector defines areflector axis A. The reflector has a neck 4, which is secured in ascrew-type base 5. As its reflective surface, it has an array oftrapezoid-like facets 6 (FIG. 2). The individual facets are portions ofcylinders, whose edges abut one another. The arc length of the edge 6bof the facet pointing toward the reflector opening is greater than thatof the edge 6a pointing toward the apex 6c. Overall, the reflector isformed of 17 rows of facets, and the first and last rows have facets ofa different structure. The arrangement of the cylindrical facets can beseen better in the plan view and side view of FIGS. 2a and 2b,respectively, which show only the reflector.

The halogen incandescent lamp 2 generally located coaxially with axis Ain the reflector 3, has a radiant body 7 bent into a W, which isretained by five mount wires 8, which are anchored in the pinch. Theluminous sections 9 of the radiant body are oriented approximatelyparallel to the reflector axis A, but not along the axis A. The luminoussections 9 are inclined by a maximum of 10° from the reflector axis A.The reflector opening is covered by a lens 15.

FIG. 3 shows the light distribution of a lamp with cylindrical facetswhose axis of symmetry includes the reflector axis. The homogeneity issubstantially better than in a similar lamp whose cylindrical facets(FIG. 4) are located transversely to the reflector axis.

FIG. 5 shows still another example for an advantageously usable lamp 2,having a W-shaped radiant body 7' with four luminous sections 9. Theinner sections 9a are approximately equal in length to the outersections which do not coincide with axis A, 9b. None of these sectionsis inclined by more than 15° from the reflector axis A.

The facets according to the invention are each adapted ot the radiantbody. In principle, the directrix of the cylindrical facet surface canbe chosen as circular, but also as elliptical, parabolic or hyperbolic.The term "directrix" is here used in the engineering sense, that is, thecurve along which a line, extending therefrom, moves to generate asurface. When this line, as it moves, remains parallel to itself, itwill generate a cylindrical surface; if it is inclined, a conicalsurface (see: Adler, "The Theory of Engineering Drawing", Van Nostrand,Copyright 1912, 1915). The generatrix of the facet can be locatedparallel to the axis of symmetry of the facet, or it may be inclined toit in the manner of a truncated cone.

The axis of symmetry mentioned here, on being projected onto eachcylindrical surface, divides that surface into two mirror-symmetricalhalves.

In the case of a circular generatrix, this axis is defined by the centerpoint of the circle; in an elliptical generatrix, it is defined by themiddle point between the two foci, for instance, and so forth.

Typically, the jacket face of the cylindrical facet is oriented parallelto the axis of symmetry of the facet. This does not, however, precludethe possibility that the jacket face may, in cone-line manner, beinclined from the axis of symmetry.

We claim:
 1. A reflector-incandescent lamp combination, comprisingareflector (3) defining a reflector axis (A) and a lamp (2), said lamphaving a radiant body (7) oriented in a plane substantially axially oraxially parallel to the reflector, said reflector (3) having areflective surface which is formed substantially of trapezoid-likefacets (6), wherein the majority of the facets comprise convexly curvedcylindrical surfaces with an associated axis of symmetry, each axis ofsymmetry being located in a plane that includes the reflector axis (A),wherein the radiant body (7) has at least two luminous sections (9), andwherein said at least two of said luminous sections are located in thelamp (2) approximately axially parallel to, but not coincident with,said reflector axis (A).
 2. The reflector-incandescent lamp combinationof claim 1, wherein the axes of symmetry of the cylindrical surfaces areoriented approximately parallel to the reflector axis (A).
 3. Thereflector-incandescent lamp combination of claim 1, wherein the lamp israted for operation with a voltage of at least 80 V.
 4. Thereflector-incandescent lamp combination of claim 1, wherein the luminoussections (9) comprise a filament coil, andwherein the coil has twoapproximately axially parallel sections.
 5. The reflector-incandescentlamp combination of claim 4, wherein the coil forms a "W" or a "V" whenviewed in the direction of an apex of the reflector is at the top. 6.The reflector-incandescent lamp combination of claim 1, wherein theluminous sections (9) of the radiant body (7) are inclined by at most15° from the reflector axis (A).
 7. The reflector-incandescent lampcombination of claim 6, wherein the luminous sections (9) of the radiantbody (7) are inclined by less than 10° from said reflector axis (A). 8.The reflector-incandescent lamp combination of claim 1, wherein the lampis a halogen incandescent lamp.
 9. The reflector-incandescent lampcombination of claim 8, wherein the lamp (2) terminates in a pinchseal;and the radiant body (7) is retained in the lamp in said pinchseal, or in a mount that is devoid of quartz beams.
 10. Thereflector-incandescent lamp combination of claim 1, wherein thegeneratrix of the cylindrical surface extends parallel to its own axisof symmetry, or is inclined to such an axis in the manner of a truncatedcone.
 11. The reflector-incandescent lamp combination of claim 1,wherein the directrix of the cylindrical facet surface represents aportion of a conical section circle.
 12. The reflector-incandescent lampcombination of claim 11, wherein the directrix of the cylindrical facetsurface represents a portion of a circle, an ellipse, a parabola or ahyperbola.
 13. The reflector-incandescent lamp combination of claim 11,wherein each cylindrical surface of the facets is bounded intrapezoid-like manner by four edges;and wherein two edges are defined bydirectrices (6a, 6b) and two further edges are defined as straight linesconnecting the ends of said directrices.